Tracking and detection of epileptiform activity in multichannel ictal EEG using signal subspace correlation of seizure source scalp topographies

Conventional methods for monitoring clinical (epileptiform) multichannel electroencephalogram (EEG) signals often involve morphological, spectral or time-frequency analysis on individual channels to determine waveform features for detecting and classifying ictal events (seizures) and inter-ictal spikes. Blind source separation (BSS) methods, such as independent component analysis (ICA), are increasingly being used in biomedical signal processing and EEG analysis for extracting a set of underlying source waveforms and sensor projections from multivariate time-series data, some of which reflect clinically relevant neurophysiological (epileptiform) activity. The work presents an alternative spatial approach to source tracking and detection in multichannel EEG that exploits prior knowledge of the spatial topographies of the sensor projections associated with the target sources. The target source sensor projections are obtained by ICA decomposition of data segments containing representative examples of target source activity, e.g. a seizure or ocular artifact. Source tracking and detection are then based on the subspace correlation between individual target sensor projections and the signal subspace over a moving window. Different window lengths and subspace correlation threshold criteria reflect transient or sustained target source activity. To study the behaviour and potential application of this spatial source tracking and detection approach, the method was used to detect (transient) ocular artifacts and (sustained) seizure activity in two segments of 25-channel EEG data recorded from one epilepsy patient on two separate occasions, with promising and intuitive results.     

Tracking and detection of epileptiform activity in multichannel ictal EEG using signal subspace correlation of seizure source scalp topographies

Conventional methods for monitoring clinical (epileptiform) multichannel electroencephalogram (EEG) signals often involve morphological, spectral or time-frequency analysis on individual channels to determine waveform features for detecting and classifying ictal events (seizures) and inter-ictal spikes. Blind source separation (BSS) methods, such as independent component analysis (ICA), are increasingly being used in biomedical signal processing and EEG analysis for extracting a set of underlying source waveforms and sensor projections from multivariate time-series data, some of which reflect clinically relevant neurophysiological (epileptiform) activity. The work presents an alternative spatial approach to source tracking and detection in multichannel EEG that exploits prior knowledge of the spatial topographies of the sensor projections associated with the target sources. The target source sensor projections are obtained by ICA decomposition of data segments containing representative examples of target source activity, e.g. a seizure or ocular artifact. Source tracking and detection are then based on the subspace correlation between individual target sensor projections and the signal subspace over a moving window. Different window lengths and subspace correlation threshold criteria reflect transient or sustained target source activity. To study the behaviour and potential application of this spatial source tracking and detection approach, the method was used to detect (transient) ocular artifacts and (sustained) seizure activity in two segments of 25-channel EEG data recorded from one epilepsy patient on two separate occasions, with promising and intuitive results.     

癫痫性痉挛发作的头皮及颅内脑电图特点

目的：研究难治性癫痫性痉挛发作患者的头皮及颅内脑电图（EEG）特点,探讨与痉挛发作相关的EEG变化及其与发作间期放电、神经影像学之间的关系。方法：回顾性分析经外科手术治疗的11例患者的临床资料,分析头皮同步视频脑电图（V-EEG）。此11例患者均行术中皮层EEG监测30～60min,其中4例术前行颅内电极长程EEG监测。结果：8例患者表现为双侧基本对称的痉挛发作,发作期头皮EEG为全导高波幅慢波、尖波伴低波幅快波活动或广泛低波幅快波活动发放;另3例患者表现为一侧肢体的痉挛发作,EEG为局灶性棘慢波发放。术中皮层监测5例患者为反复的、暴发出现的多棘波活动,2例患者见持续性的棘波、尖波活动,4例未见明显的癫痫样电活动。4例行颅内电极监测者发作期EEG表现,2例为“前导性”的高波幅棘波伴随20Hz左右的低波幅快波发放;另2例为局灶性低波幅快波活动并迅速扩散,无“前导性棘波”。手术切除“前导性棘波”或反复性、节律性痫样放电的皮层可消除发作。结论：在一部分癫痫性痉挛发作患者,其痉挛发作可能因新皮层局灶的电发放点燃,颅内EEG如果存在前导性的棘波,这个棘波部位可能是促发痉挛发作的点燃灶。完整切除术中监测呈现反复性、节律性痫样放电的皮层可取得较好的手术效果。     

癫癎发作前期脑电变化特征分析

目的 :探讨癫临床发作前期的脑波变化特征。方法 :采用Video -EEG监护系统对 82例癫患者进行脑电和行为监测 ,监护系统自动记录发作时的行为表现及脑电变化。结果 :82例中共监测到 16例临床发作 ,发作期脑波被大量肌电干扰不易分辨 ,发作前期脑波有如下几种表现 :①背景波先变为低幅快波 ,波幅渐升高 ,或背景为低幅慢波 ,发作前 5～ 14秒内波幅升高频率增快 ,但仍为慢波 ;②发作前背景节律变慢 ,波幅升高 ;③发作前背景节律不变 ,仅波幅明显升高 ;④出现样放电波形。结论 :癫发作前脑波频率增快或波幅升高 ,应视为与癫发作有密切关系的现象。     

发作期及发作间期痫性放电对癫痫的诊断价值

目的探讨发作期及发作间期脑电图对癫痫诊断的意义。方法对５６例癫痫患者常规脑电图（ＲＥＥＧ）与２４ｈ脑电图（ＡＥＥＧ）进行比较研究。结果①ＲＥＥＧ的阳性率为３０％，而ＡＥＥＧ的阳性率为８６％；②不同类型癫痫在发作期和发作间期大脑活动的规律和特点，ＲＥＥＧ无１例记录到癫痫发作，而ＡＥＥＧ有２７例（４８％）记录到癫痫发作全过程的大脑电活动变化。结论发作期的ＥＥＧ对确定癫痫类型有重要意义，全身性癫痫在发作的同时发作波在两侧半球同时出现，而部分性发作患者在临床发作的同时ＥＥＧ常局限在某一脑叶有单个棘波发放，此棘波处是癫痫的病灶的部位，这种局限棘波可扩散至全脑而临床出现全身阵挛发作，此类患者为部分性癫痫并非全身性癫痫。     

应用因果分析方法对癫痫发作间期头皮脑电信号进行致痫灶定侧

目的利用因果分析方法对癫痫发作间期的头皮脑电信号进行致痫灶定侧。方法在频域因果分析方法——自适应直接传递函数（ADTF）的基础上提出功率谱加权ADTF（psADTF）法,以给定频段内信号的功率谱对ADTF的标准化做加权,以适应不同癫痫波频域信息不同的特点。利用该方法对2组共30例患者的头皮脑电信号进行分析,含组1癫痫手术患者15例,组2门诊癫痫患者15例。其中组1患者共截取癫痫波样本数104个,组2患者共截取癫痫波样本数98个。结果组1患者通过psADTF分析对致痫灶定侧与手术侧一致的有96个,平均单个癫痫波致痫灶定侧准确率可达92％;组2患者通过psADTF分析对致痫灶定侧与专家判读结果一致的有94个,平均单个癫痫波致痫灶定侧准确率达96％。结论发作间期头皮脑电癫痫波信号的psADTF分析能够很好地辅助临床致痫灶定侧。     

老年人迟发性癫Xian发作的临床及脑电图分析

目的：探讨老年人迟发性癫Xian发作的临床及脑电图特点。方法：回顾性分析80例老年人迟发性癫Xian的临床及脑电图资料。结果：癫Xian发作的可能因为脑血管病41例（脑梗死30例、脑出血11例）,脑肿瘤19例,脑外伤4例,脑萎缩8例。癫Xian发作的类型为全身强直阵挛发作48例;强直阵挛发作持续状态2例,失神发作6例,单纯运动性发作17例,单纯体感性发作7例。脑电图正常7例,异常73例。异常脑电图主要表现为弥漫性慢波活动22例,局限于一侧半球的慢波活动34例,散在或阵发性棘波、尖波或棘慢、尖慢综合波49例。结论：脑血管病（脑梗死、脑出血）、脑肿瘤是老年迟发性癫Xian发作的主要原因。癫Xian发作以全身强直阵挛发作为主。脑电图异常率高,主要表现为在弥漫性慢波活动基础上出现癫Xian样放电。     

A statistical approach to computerized EEG: Preliminary data on control subjects and epileptic patients

Factor Analysis represents an important method of extracting salient features from EEG data condensing functional as well as spatial informations in a few factors and so reducing redundancy of multi-channels computerized EEG data. A 16-channel computerized frequency analysis of background brain electrical activity during 3 functional conditions (eyes closed, eyes open and hyperventilation) were performed in 2 groups, 50 healthy subjects and 14 epileptic patients with generalized seizures. The differences in each frequency band between the 2 groups have been assessed by means of factor scores. Factor scores differences between control and epileptic patients have been found in theta and alpha frequency bands. These interictal EEG abnormalities were more evident in epileptic patients. This preliminary study shows the confirmatory capability of Factor Analysis and its usefulness in managing and comparing computerized EEG data.     

Application of singular value cecomposition to topographic analysis of flash-evoked potentials

Singular value decomposition is a robust numerical method for decomposing a matrix of multichannel EEG or EP data into a sharply reduced set of features with corresponding waveform, amplitude, and spatial vectors. In 19 normal subjects aged 19 to 40 years, the three largest features computed by the SVD algorithm accounted for 93-98 percent of the total variance of the averaged flash-evoked potential. There was good separation of major brain areas as well as clustering of related electrode sites. Orthogonal rotation of the three spatial vectors is essential to see clustering of brain areas across subjects. Three-dimensional display showed the regular presence of orthonormal occipital, frontopolar, and vertex spatial vectors. Since the spatial feature vectors cluster tightly and yet are orthonormal, statistical comparison of patients with normal control groups will be facilitated.     

结节性硬化所致婴儿痉挛症发作期脑电局灶或一侧优势现象31例报告

目的：探讨结节性硬化症（TS）所致婴儿痉挛症患者发作期脑电活动局灶改变及其分布优势侧的特征现象,以及与术后疗效的关系。方法：回顾分析了31例TS术前脑电图定位在发作期呈现的局灶、一侧多灶,或双侧均有病灶而以一侧占优势的脑电图现象,并结合术后随访结果对比分析其差异。结果：局灶性放电（单灶）6例,一侧多灶14例,双侧改变以一侧占优势的11例。经统计学处理,局灶与一侧多灶比较差异有显著意义（P〈0．05）．与两侧均有以一侧占优势相比差异有极显著意义（P〈0．01）。结论：TS所致婴儿痉挛症患者间歇期表现为多灶性弥散放电甚至高度失律,但发作期起源灶相对明确,呈现局灶、一侧多灶或者两侧均有以一侧占优势,给外科干预提供有力的依据,并获得良好疗效,尤其对于发作期局灶改变者效果尤好。     

睡眠脑电的奇异系统分析

奇异系统分析具有抑制噪声的效果,并且方法简单,计算量小.睡眠脑电的奇异系统分析表明,第一主成分含量明显反映了睡眠状态差异:在清醒时最低,随着睡眠加深逐渐增加,但在REM期时介于S1期和S2期之间.这一结果基本不受个体、数据长度、嵌入维数以及延迟时间的影响.     

Quantitative analysis of epileptic discharges

Summary The methods for analysing the EEG epileptiform activity are discussed and compared. Particular emphasis is placed on studying interictal spike activity recorded from scalp. The results of these analyses should be interpreted in terms of underlying physiological events. An example is the hypothetical model of benign rolandic epilepsy of childhood.     

癫痫患者的脑电图与CT对比研究

目的：探索ＥＥＧ和ＣＴ在癫痫的诊断、分型和病因方面的意义。方法：对１３７９例癫痫进行ＥＥＧ常规描记和脑ＣＴ扫描。结果：１３７９例中原发性癫痫９８５例（７１４３％），继发性癫痫３９４例（２８５７％）。ＣＴ异常率４６１９％；ＥＥＧ异常率７４２６％，痫波检出率２３４７％。ＥＥＧ以局灶性或弥漫性慢波增多为主。ＥＥＧ和ＣＴ的符合率８０９５％。结论：ＥＥＧ对癫痫的分型和原发性癫痫的检出有重要价值，而ＣＴ则是查找继发性癫痫病因的有效方法     

改进G-P算法与睡眠脑电的关联维

脑电的非线性参数能有效表达大脑的不同生理状态,不同睡眠期脑电的关联维数不同.但用G- P算法求关联维数存在抗干扰能力较差、可靠性不稳定、运算量巨大等缺点.先对相空间进行奇异谱分析,进而对原始相空间进行旋转,使其成为正交的等效空间,然后再使用G- P算法.改进后的算法能有效地抑制噪声干扰,降低相空间规模,减少运算复杂性,在睡眠脑电的关联维数计算上效果良好.     

发作期同步视频EEG与EMG联合监测在鉴别点头癫痫发作类型中的意义

目的：评估发作期同步视频脑电图（V—EEG）及表皮肌电图（EMG）联合监测在诊断和鉴别以点头发作（head nodding attack）为临床表现的癫痫的意义。方法：应用64道尼高力-one视频脑电图仪记录长时间V—EEG并同时在目标肌肉皮肤上安装盘状电极同步记录表面EMG进行分析。人组标准：①明确是癫痫患者;②V—EEG监测后明确癫痫发作临床表现符合在坐位表现为点头,伴或不伴其他临床表现。结果：9例患者共记录到107次临床发作：轴肌强直发作19次,短暂性强直发作8次,不典型失神发作1次,典型失神2次,全面性强直发作2次,全面性强直阵挛发作4次,轴肌肌阵挛发作23次,眼睑肌阵挛11次,肌阵挛失神发作26次,肌阵挛失张力发作3次,失张力发作2次,右侧上肢肌阵挛发作1次,强直性痉挛发作5次。发作时临床表现符合坐位点头动作的共86次发作。结论：发作期同步视频EEG—EMG能明确诊断并鉴别以点头发作为临床表现的癫痫发作类型,如轴肌肌阵挛发作、肌阵挛失神发作、肌阵挛一失张力发作、失张力发作、痉挛发作、强直痉挛发作及短暂性强直发作;癫痫患者行头皮V—EEG监测时同步记录表面EMG,从时间及空间参数上有助于量化分析,结合临床表现及视频分析有助于鉴别临床表现以点头为主的癫痫发作类型。     

Precision of dipole localization in a spherical volume conductor: A comparison of referential EEG,magnetoencephalography and scalp current density methods

Summary In this study, we determined the influence of dipole orientation, dipole location, and number of recording sites on the precision of dipole localization in a spherical volume conductor. We compared localization from referential EEG (R-EEG), scalp current density EEG (SCD-EEG) and magnetoencephalography (MEG). Dipole orientation had a small influence on the precision of dipole localization for R-EEG and SCD-EEG. Dipole location relative to the recording sites, dipole depth, and number of recording channels strongly influenced the precision of dipole localization. Assuming equal signal to noise conditions for each recording method, MEG and SCD-EEG had a similar precision for dipole localization of a single tangential dipole source and both methods were more precise than R-EEG. However, SCD-EEG was inferior to MEG for distinguishing a single tangential current source from a pair of deeper radial current sources. In summary, these results suggest that the MEG will be most useful for localization of multiple simultaneous dipole sources.     

18例复杂部分性癫痫发作患者同步录像脑电图监测报告

目的：探讨同步录像脑电图（Video-EEG）在复杂部分性癫痫发作诊断中的应用价值。方法：利用ZN8000型EEG仪对临床确诊的18例复杂部分性发作患者进行脑电和行为监测,监测时间2．5～28h平均用18.8h。结果：共监测到93次临床发作,睡眠中发作54次,清醒时发作39次,发作持续时间7～120s,平均34．8s。发作时的临床表现：双眼向前或向一侧凝视11例,头向一侧转动9例,一侧面部或肢体抽搐9例,行为或口咽自动症6例,精神症状5例,姿势性发作5例,对发作过程不能回忆15例。发作期EEG示癫病样放电（棘波、尖波、棘慢、尖慢综合波）12例,阵发性高幅慢波5例,未见异常1例,EEG异常率95％。发作间期EEG示中高幅阵发性慢波3例,阵发性痫样放电9例,未见异常6例,EEG异常率65％。结论：Video－EEG对复杂部分性癫痫发作有重要诊断价值,痫样放电与临床发作密切相关。     

儿童失神癫(癎)脑电图的多尺度特征

目的:研究儿童失神癫癎脑电图的多尺度定量特征。方法:对15例失神癫癎患儿10次临床发作和20次亚临床癎样放电的脑电图进行子波分析,提取失神癫癎发作过程中脑电信号的多尺度定量典型特征,与发作前10 s及发作后10 s的脑电信号进行比较,并与12例正常同龄儿童脑电图进行比较。结果:研究显示儿童失神癫癎发作过程中脑电信号的多尺度典型特征主要表现为12尺度(对应频率3 Hz)的节律性活动显著增强,发作时20尺度(低频大尺度,对应频率0．12 Hz)结构与频率3 Hz的结构具有非正常的跳跃式尺度关系,3 Hz节律性棘慢复合波与大尺度(频率1 Hz以下)背景低频放电结构共同存在。发作过程中分尺度功率主要集中在20尺度和12尺度,其演变规律为20尺度能量逐渐减低,12尺度能量逐渐增加。10次临床发作的脑电信号均显示上述特征。发作前10 s和后10 s的脑电多尺度信号中仍然存在隐性的3 Hz棘慢复合波成分,与一般认为3 Hz棘慢复合波突起突止不同．而从传统的脑电图上无法分辨出发作前后的这些多尺度细节的定量特征。亚临床癎样放电的多尺度特征与发作期无明显差别,但持续时间短。结论:子波分析作为一种新的信号分析方法,适合于脑电信号的分析,可以获得比传统视觉脑电图更多的定量信息。通过对失神癫癎患儿的脑电信号进行子波分析,得到其发作过程中典型的多尺度定量特征,有助于失神癫癎发作的临床辅助诊断、预后评价以及神经电生理机理的基础研究。